Thermomechanical Models for Amorphous Polymers Accounting for Shear Yielding and Crazing

• Applicants: Dr.-Ing. Hüsnü Dal; Professor Dr.-Ing. Marc-André Keip, since 10/2016
• Subject Area: Mechanics
• Term: from 2007 to 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 36678517

Industrial applications of amorphous polymers such as polycarbonates or polystyrenes cover the automotive industry, the medical technology and the production of high-tech electronic devices. In this context, the construction of predictive continuum-based models for the response of polymeric devices under non-isothermal loading conditions is of high importance for the technological design as well as the production of new materials. Goal of the research project is the development of a fully coupled thermo-viscoplastic material description for amorphous polymers that inherently embodies the rate- and temperaturedependent micro structure evolution. The models to be developed must account for microphenomena such as the competition of micro-shear yielding and crazing. The evolution of these micro-phenomena is associated with molecular mechanisms involving disentanglement, scission, plastic orientation of the constituent macromolecules. The outgrowth on the overall macro-level determines the brittle to ductile transition of the material. The micromechanical effects are intended to be described by two new thermomechanical model concepts, a (i) meso-scale approach for the resolution of small-scale phenomena, where the crazing is modeled by a fracture-type cohesive zone theory and a (ii) hybrid micro-macro approach for large-scale analyses, where the crazing is modeled by macroscopic structural tensors. The overall result of the project will be new theoretical and algorithmic formulations for predictive large-scale analyses of thermomechanical deformation processes of amorphous polymers. The project is accompanied by an experimental program and model parameter identification procedures.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Professor Dr.-Ing. Christian Miehe, until 9/2016 (†)